The structure has an L-shaped supporting element (2) juxtaposed and superimposed such that a horizontal lower face (5) of the element forms a base of volume to receive a plantation substrate and top of the volume simultaneously to receive the plantation substrate. A connection unit (13) connects the support elements, and is juxtaposed and/or superimposed between a front edge (8) of the horizontal lower face of the support elements and an upper and lower edge of a vertical gridded closing element (3).
